NEW YORK (Reuters Health) - In liver transplant recipients with cytomegalovirus infection, antiviral immune reactions appear to limit the cytopathic effect of the virus on the liver, according to a study in the May issue of the Journal of Medical Virology.

Dr. A.L. Bissinger of the Universitatsklinikum Tubingen in Tubingen, Germany and colleagues explain that it has never been clear whether antiviral immune responses limit the extent of tissue damage from cytomegalovirus or rather increase it.

In the study, the investigators performed immunohistochemical analysis on 84 liver biopsy specimens from 74 patients and correlated the extent of viral replication with the cytomegalovirus antibody status of the patient and the organ donor.

In 25 of the biopsy specimens, the researchers documented the presence of cytomegalovirus immediate early antigens. According to their paper, the median extent of infection was 0.33 infected cells per millimeter squared of liver tissue.

In patients with primary infection, however - that is, patients who acquired their infection from an infected donor - the extent of organ infection was three times higher than in patients who were seropositive before transplant.

On the other hand, patients with pre-existing immunoreactivity had a greater extent of inflammatory infiltrates in areas of infected liver cells.

Their findings, the authors say, indicate "the protective nature of a pre-existing cytomegalovirus-specific immune response."

Also, they conclude, their results favor "the assumption that the immune response to cytomegalovirus is effective in restricting viral spread in the liver."